KR101165120B1 - Method for processing harq in a mobile communication system - Google Patents

Abstract

The present invention multiplexes and transmits a distributed resource channel for obtaining diversity gain and a localized resource channel for obtaining frequency selective scheduling gain in an orthogonal frequency division multiple access mobile communication system. In addition, the present invention relates to a method for improving resource utilization efficiency and improving performance by changing a HARQ method according to a multiplexing method.

Multiple access system, multiplexing, hybridization method, complex retransmission, persistent allocation, non-persistent allocation, S-HARQ, RAS-HARQ, LRCH, DRCH

Description

Complex retransmission method in mobile communication system {METHOD FOR PROCESSING HARQ IN A MOBILE COMMUNICATION SYSTEM}

1 is a configuration diagram of a typical LRCH and DRCH,

2 illustrates an example of a general DRCH;

3 is a view for explaining a first multiplexing method;

4 is a view for explaining a second multiplexing method;

5 is a flowchart illustrating a complex retransmission method in a mobile communication system according to an embodiment of the present invention.

The present invention relates to a hybrid automatic repeat request (HARQ) method in a mobile communication system, and more particularly, to a method of processing HARQ according to a multiplexing method and a resource allocation method in an orthogonal frequency multiple access system. will be.

In general, a wireless communication system refers to a method of providing a user to perform communication regardless of a specific place using a terminal. Such a wireless communication system has been developed to accommodate a large number of users using various multiple access schemes. A typical method of the wireless communication system is a code division multiple access (CDMA) scheme. The code division multiple access scheme has been developed to process data at a relatively high speed, beginning with voice communication. As such, the development of code division multiple access is caused by the rapid development of technology with the demand for faster data transmission by users. The code division multiple access method has been commercialized due to the development of technology, and most standards of 3G mobile communication systems have been decided.

However, due to the limited resources used in the code division multiple access scheme, there is a problem that the limit for transmitting data at high speed is reached. Nevertheless, the transmission rate of data required by users continues to increase. Therefore, in the field of wireless communication, various researches and attempts have been made to transmit data at a higher speed.

In one direction of the above-described research, research has been conducted on a method of performing communication using an Orthogonal Frequency Division Multiple Access (hereinafter, referred to as "OFDMA") scheme. In the OFDMA scheme, a plurality of channels are formed using frequencies having orthogonality, and at least one or more channels are allocated to each user to transmit data. Next, the process of communication in the OFDMA scheme will be briefly described.

In the OFDMA scheme, communication uses a scheme of allocating subchannels of uplink and downlink. That is, the communication is performed by dividing the uplink time and the downlink time within a specific time and allocating the channel for each user within the time. In addition, in the cellular mobile communication system based on the OFDMA, two types of operation methods may be largely classified according to an operation method of available frequencies. The available frequency operating method means a method according to a frequency reuse factor. Let's look first at the first and most common way. The first method uses a frequency reuse factor greater than 1, such as 3 or 7.

In general, a channel in an OFDMA scheme is composed of a physical channel in the form of a localized resource channel (hereinafter referred to as "LRCH") and a distributed resource channel (hereinafter referred to as "DRCH").

The LRCH is a time-frequency domain resource composed of consecutive subcarriers of the same position in several consecutive OFDM symbols. This resource is a resource existing to select and allocate regions having good channel conditions to a terminal having a good channel environment in a frequency selective channel environment.

The DRCH is a channel that is allocated to a terminal to obtain frequency domain diversity because the DRCH is a resource composed of a set of subcarriers evenly distributed in a specific frequency time domain.

FIG. 1 is a diagram illustrating an example in which resources are allocated in the manner of LRCH and DRCH in an OFDM system.

The entire frequency space consists of a plurality of LRCHs or DRCHs and the total number may be changed as necessary. The LRCH divides the entire band into a plurality of subbands on the frequency axis and defines each as one LRCH. Each LRCH is used for subband scheduling.

2 is a diagram illustrating an example in which resources are allocated by the DRCH scheme in an OFDM system.

The minimum unit of the time domain is an OFDM symbol, and in FIG. 2, seven OFDM symbols constitute one minimum transmission unit (eg, a slot). The vertical axis is the frequency domain and the minimum unit is the subcarrier. One subcarrier is configured to belong to one DRCH for every eight subcarriers. Each DRCH is marked differently. In the illustrated example, each channel is repeated once every eight subcarriers, which is called a repetition period. If the repetition period is N, the example of FIG. 2 is N = 8. Each channel has a different starting position for each OFDM symbol, which may be represented as an offset. In the case of DRCH 1, the offset is 0 for the first OFDM symbol, the offset is 3 for the second OFDM symbol, and the offset is 6 for the third OFDM symbol. The illustrated slot has an offset sequence of {0,3,6,1,5,2,7} according to the OFDM symbol order.

That is, as described above, the entire band may consist of LRCH or DRCH during one slot period. The two channels may be used simultaneously in one system. Hereinafter, a method of multiplexing the two physical channels will be described with reference to FIGS. 3 and 4.

3 is a diagram for explaining a first multiplexing method.

In the first multiplexing method described in FIG. 3, the DRCH is defined over the entire band, and the LRCH is defined as a frequency time resource in a predefined sub-band, wherein the frequency time allocated to the DRCH in the sub-band. It is a method of configuring an LRCH excluding resources (one subcarrier in one OFDM symbol).

In this case, as the number of transmitted DRCHs increases, the number of frequency time resources punched due to DRCH in the LRCH region increases. On the other hand, the remaining DRCH resources after being used as DRCH can be used as LRCH resources naturally, which is a multiplexing method that can efficiently use the resources.

4 is a diagram for describing a second multiplexing method.

The second multiplexing method of FIG. 4 configures a DRCH in the remaining space after first securing a physical channel allocated to the LRCH. This method also first configures the same number of LRCHs in the entire band. First, the LRCH is allocated to the user, and the remaining space is grouped to reconstruct the DRCH. In this case, since the DRCH and LRCH regions are strictly separated, the amount of resources allocated to the LRCH users does not change even when the number of users using the DRCH channel is large. However, when the number of DRCHs is small, the remaining frequency time resources other than the LRCH must be filled with the DRCH, so there is a problem in that resources are wasted when no user needs the DRCH.

Accordingly, an object of the present invention is a hybrid retransmission method and apparatus for efficiently using resources according to a multiplexing mode and a resource allocation method used in an orthogonal frequency division multiple access mobile communication system which combines continuous resource allocation and non-persistent resource allocation. To provide a receiving method and apparatus for.

Another object of the present invention is to provide a complex retransmission method and apparatus and a reception method and apparatus for minimizing transmission of control information in a mobile communication system which combines continuous resource allocation and non-persistent resource allocation.

The method according to the embodiment of the present invention uses an orthogonal frequency multiple access (OFDM) scheme, and the resource allocation method in a mobile communication system that transmits data in a hybrid automatic retransmission (HARQ), distributed resources to multiplex orthogonal frequency resources Determining one of a multiplexing mode of a distributed resource channel (DRCH) and a localized resource channel (LRCH), and determining whether to continuously allocate resources in every slot when the determined multiplexing mode is a DRCH. Process and, if resources are continuously allocated to every slot, resources are allocated in a synchronous HARQ (S-HARQ) scheme, and if the resources are not continuously allocated to every slot, an early termination of transmission occurs during HARQ transmission. If resources need to be recycled, the method includes allocating resources in a resource adaptive asynchronous HARQ (RAS-HARQ) scheme.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions of the present invention, and may be changed according to the intentions or customs of the user, the operator, and the like. Therefore, the definition should be based on the contents throughout this specification.

Apart from physical channel definition or multiplexing, persistent resource allocation and non-persistent resource allocation can be defined in the resource allocation method. In the case of a mobile communication system supporting only a conventional voice service, a specific ratio of resources is always allocated to a specific user through fixed resource allocation. For IS-95, code assignment is an example. This saves resources for transmitting control information. On the other hand, the recently proposed HRPD system supporting packet scheduling only supports non-persistent resource allocation. This system supports the non-persistent resource allocation method because it checks the channel status of each user and allocates all resources to the users with good channel status. In this case, of course, the control channel is transmitted at every scheduling to identify which terminal should receive. The difference between the two resource allocations described above can also be attributed to the differences in the applications mainly used. There was a difference in resource allocation because of the differences between voice calls requiring continuous transmission and best effort data transmission requiring large amounts of transmission.

The mobile communication system currently under discussion is designed to support both voice, video, and best effort traffic. Therefore, both resource allocation methods are discussed. The basic assumptions are as follows:

In the case of persistent resource allocation, if the resource allocation is performed only once, the packet may be transmitted without a control signal during the initial subpacket transmission in a specific period. In the present invention, HARQ is used for continuous resource allocation. This particular period may be fixed at 20 msec, for example. Other values are possible. If the terminal succeeds in decoding the encoder packet within 20 ms, the terminal transmits an ACK packet to the base station. Slots remaining until the next 20msec boundary may be used for other users through non-persistent resource allocation.

In the case of non-persistnet allocation, since the initial transport packet can be transmitted in an arbitrary slot, control information must be accompanied in every initial allocation. HARQ can also be used for non-persistent resource allocation.

Hereinafter, a HARQ scheme for supporting the transmission scheme will be described.

Recently, in the mobile communication system providing the packet service, the mobile terminal receiving the packet from the base station informs the base station whether the packet is successfully received, and the base station retransmits the packet that the mobile terminal did not normally receive. Technology is becoming common. In this case, the HARQ is one of a link control protocol for requesting retransmission of the packet from the base station when the mobile terminal has an error in the received packet. In general, since it is practically impossible for a mobile terminal of a mobile communication system to receive a packet transmitted through a wireless network without any distortion or noise mixed, HARQ technology proposes various packet retransmission techniques to solve this problem.

Hereinafter, some terms described herein with respect to the HARQ technology will be defined as follows.

First, "packet" means original information before encoding, and "sub packet" is transmitted at once when the encoded bit stream is divided into multiple chunks of contiguous bits. Means a chunk of bits. And "control information" means additional information other than the original information necessary for receiving the "sub packet" or "packet". Initial transmission is a subpacket transmitted first among the subpackets. The retransmission subpacket is a subpacket transmitted after the first subpacket.

HARQ technology can be largely divided into synchronous HARQ (hereinafter referred to as S-HARQ) and asynchronous HARQ (hereinafter referred to as AS-HARQ). First, the S-HARQ is characterized in that the retransmission for the initial transmission is performed at a predetermined time. Synchronous here means synchronization in the time domain. In addition, the AS-HARQ is characterized in that the time interval between the initial transmission and retransmission is performed without being determined. In the present invention, the description is based on S-HARQ, which is easy to implement and has been discussed for simple operation. It describes pure S-HARQ that can be transmitted without changing transmission resources during retransmission and resource adaptive synchronous HARQ (RAS-HARQ) that can be accompanied by changes in transmission resources during retransmission even during S-HARQ.

In the case of the S-HARQ, the time and resources for retransmission are predetermined. In the case of S-HARQ, if it is used for continuous allocation, it may be fixed until the initial transmission time. On the other hand, RAS-HARQ differs from S-HARQ in that the resources to which retransmission packets are transmitted can change if control information is transmitted together during retransmission. When RAS-HARQ is also used for continuous allocation, the time of initial transmission is fixed.

When the two HARQs are applied to an orthogonal frequency division multiple access system, data can be simultaneously transmitted through a plurality of channels during one time slot of the current orthogonal frequency division multiple access system. In the case of S-HARQ, a channel for retransmission is fixed. RAS-HARQ operates by changing the channel number if necessary for retransmission.

The system described in the present invention operates as follows.

-The base station periodically informs the terminal which multiplexing method to use.

-After determining the multiplexing method, the base station transmits a packet to the terminal using a resource allocation method and a HARQ method.

First, the case of the multiplexing mode 1 described above will be described. In the multiplexing mode 1, the DRCH is transmitted over the entire band, and the remaining resources are used by the LRCH. For this reason, when the number of DRCHs is large, the amount of resources that can be used by the LRCH is reduced. Therefore, the multiplexing mode 1 may be appropriately used when the number of DRCHs is small. Since all remaining resources used as DRCH can be used as LRCH, it is efficient in terms of resource recycling. The remaining resources can be used as DRCH again. This is necessary when supporting high speed users.

In conjunction with the resource allocation aspect, applications where multiplexing mode 1 is delay sensitive, such as VoIP, and require more than a fixed rate, are transmitted using persistent allocation. In this case, since HARQ is used, early termination may occur, and the remaining resources may be used by other users using LRCH or DRCH in a non-persistent allocation method. In this case, when the resources remaining after the early termination are allocated to the LRCH, DRCHs that are not used naturally are allocated to the LRCH, so that the resources remaining naturally without special signaling can be used for scheduling.

When LRCH is used, frequency selective scheduling is performed, so it is necessary to continuously transmit the current subband even when retransmitting. In this case, therefore, it is appropriate to transmit using S-HARQ. On the other hand, if the resource remaining after the early termination is reassigned to the DRCH, retransmission packets of non-persistent allocation and initial transmission of persistent allocation may cause conflicts using the same resource. Need to move RAS-HARQ is needed to support this behavior.

In other words, since the situation of using multiplexing mode 1 is a situation where the number of DRCH users is small, the persistent allocation is terminated early, and even though some resources are empty, the remaining resources can be allocated using LRCH. The efficiency of resource utilization can be improved while maintaining the same level. In addition, when using the remaining resources by using the DRCH, HARQ operation is required to move the location of resources due to the possibility of resource collisions of continuous initial transmission and non-persistent transmission.

The case of the multiplexing mode 2 will be described. In this case, part of the entire band is pre-allocated for LRCH use. The DRCH is reconfigured and transmitted in resources except the LRCH. This method is preferably used when the number of users using DRCH is high because DRCH does not puncture LRCH resources. One limitation of this method is that DRCH can only be used to recycle the extra resources left behind by premature termination. Furthermore, because of the large number of users in DRCH, there will be many early terminations, and the resources allocated for DRCH will be fragmented at any given moment. In other words, the resources that are being used and the resources that are available will not be present in a contiguous cluster, but will be a mixture of resources that are not used disorderly. In this case, when reallocated fragmented resources to the UE individually, a lot of signaling overhead is required. Therefore, in this case, in order to increase the efficiency of resource allocation, it is necessary to move a plurality of available resources to one place and signal them.This operation of separating the available resources from the used resources and relocating them through RAS-HARQ is necessary. Can be. For example, suppose that persistent allocations were allocated from DRCH 1 to 10, of which DRCH 1, 3, 6, 7, and 9 were terminated prematurely. In this case, in order to effectively recycle the remaining channel after the early termination in the next slot, it may be necessary to collect the remaining resources together and allocate them to specific terminals at once. In other words. If DRCH 2, 4, 5, 8, 10 to be transmitted to the next slot is moved to 1, 2, 3, 4, 5 respectively, 5, 6, 7, 8, 9, 10 can be fragmented at a desired rate and used for other terminals. Could be. Multiplexing mode 2 has the advantage of efficiently reallocating the remaining resources by preventing fragmentation of resources due to early termination in every slot.

The above two multiplexing modes, resource allocation schemes, and HARQ schemes used are shown in Table 1 below.

5 is a flowchart illustrating a complex retransmission method in a mobile communication system according to an exemplary embodiment of the present invention. A hybrid retransmission method in a mobile communication system according to an embodiment of the present invention will be described with reference to FIG. 5.

The base station determines in step 501 whether the initial transmission packet. If it is not the initial transmission packet, it is in a waiting state. However, in the case of the initial transport packet, the base station checks the multiplexing mode for the initial transport packet in step 503. That is, it is determined whether the DRCH is the multiplexing mode 1 for puncturing the resources of the LRCH for the initial transport packet.

If the multiplexing mode 1, the base station determines whether the continuous allocation in step 505. If the continuous allocation, the base station operates in S-HARQ using the DRCH in step 507.

However, in case of non-persistent allocation, that is, non-persistent allocation, the base station determines whether the available DRCH channel is used after the early allocation is terminated early in step 509. After the persistent allocation is terminated early, if the available DRCH channel is used, RAS-HARQ is used in step 513. If the continuous allocation is not an early terminated resource and the original non-persistent allocation, the base station uses S-HARQ in step 511. If the LRCH is allocated, the base station uses S-HARQ regardless of whether the channel is terminated early.

On the other hand, if the DRCH is not the multiplexing mode 1 that punctures the LRCH resource in step 503, the base station determines in step 515 whether the resource for the LRCH and the DRCH resource are the multiplexing mode 2 divided into subband units.

If not in the multiplexing mode 2, the base station terminates. However, in the multiplexing mode 2, the base station determines whether the DRCH is used in step 517. When using the DRCH, the base station uses RAS-HARQ in step 513. However, if the DRCH is not used, the base station uses S-HARQ in step 519.

In the above description, the present invention has been described with reference to preferred embodiments, but the present invention is not necessarily limited thereto, and one of ordinary skill in the art to which the present invention pertains may have various modifications without departing from the technical spirit of the present invention. It will be readily appreciated that branch substitutions, modifications and variations are possible.

In the present invention that operates as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

The present invention can increase resource usage efficiency by operating a suitable H-ARQ scheme according to whether a continuous resource allocation or a non-persistent resource allocation scheme is used in a system supporting two multiplexing modes.

In addition, the present invention can efficiently utilize resources according to a multiplexing mode and a resource allocation method used in an orthogonal frequency division multiple access mobile communication system that combines continuous resource allocation and non-persistent resource allocation.

In addition, the present invention can minimize the transmission of control information in a mobile communication system that combines continuous resource allocation and non-persistent resource allocation.

Claims (5)

In the resource allocation method of the complex retransmission method in a mobile communication system using an Orthogonal Frequency Multiple Access (OFDM) method and transmitting data by a hybrid automatic retransmission (HARQ), Determining one of multiplexing modes of a distributed resource channel (DRCH) and a localized resource channel (LRCH) to multiplex orthogonal frequency resources; Determining whether to continuously allocate resources in every slot when the determined multiplexing mode is DRCH; If resources are continuously allocated to every slot, resources are allocated by synchronous HARQ (S-HARQ) method. If resources are not continuously allocated to every slot, resources are recycled when early termination of transmission occurs during HARQ transmission. If necessary, the resource allocation method of a complex retransmission method comprising the step of allocating resources in a resource-adaptive asynchronous HARQ (RAS-HARQ) method. The method of claim 1, If the resource is not continuously allocated to every slot, if the resource is not required to be recycled when the early termination of transmission occurs during HARQ transmission, further comprising the step of allocating resources in the S-HARQ method Resource allocation method of complex retransmission method. The method of claim 1, Determining whether to continuously allocate resources in every slot when the determined multiplexing mode is LRCH; If it is determined that the resource is continuously allocated to each slot, the resource allocation method of the complex retransmission method further comprising the step of allocating resources in a RAS-HARQ method. The method of claim 1, Determining whether to continuously allocate resources in every slot when the determined multiplexing mode is LRCH; Determining whether to use the remaining resources allocated to the LRCH and the remaining resources as the DRCH if the resource is determined not to be continuously allocated to each slot; If it is determined to use the remaining resources as a DRCH resource allocation method of the complex retransmission method further comprising the step of allocating resources in a RAS-HARQ method.  The method of claim 1, Determining whether to continuously allocate resources in every slot when the determined multiplexing mode is LRCH; Determining whether to use the remaining resources allocated to the LRCH and the remaining resources as the DRCH if the resource is determined not to be continuously allocated to each slot; If it is determined that the remaining resources are not to be used as a DRCH, the method further includes allocating resources in the S-HARQ method.

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